SAT Subject Biology Practice Question 130: Answer and Explanation

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Question: 130


Considering the phenotypes of generations II and II, what is the most likely genotype of the man in generation I?

A. Autozygous
B. Hemizygous
C. Heterozygous
D. Homozygous recessive
E. Homozygous dominant

Correct Answer: C


The man in generation I (I-1) must be heterozygous in order for his offspring to exhibit the trait. The affected offspring inherit only one allele from their mother, who is affected. Therefore, they must have inherited the second allele from their father.

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